Our club has a repeater in which the squelch does not work. The transmit receive works fine, but because the receiver can not be squelched the transmitter stays triggered. We have replaced the entire squelch board, and tested the squelch pot. but still have not been able to fix the problem. If anyone has experience with repeaters and can make some suggestions and recommendations? It would be appreciated.

Hello AD4U, I was just able to locate the manufacturer and model of the club repeater. It is a GE Master 2. Like I said in my original post we replaced the squelch board. The volume on the squelch board works as it should, but the squelch pot does not. We tested the pot and it operates as it should (sorry I needed to repeat myself for clarity). I have located a schematic for the repeater and the master control panel 871P1. Please let me know if anyone has some ideas I can try to fix the squelch problem with this repeater?

PS: We have access to a complete extra repeater of the same type for parts.

This sounds like more of a controller problem than a repeater problem. Have you verified that the squelch board puts out a COS signal to the controller? Are you sure the COS signal is actually making it to the controller? Is the polaritry of the controller COS line set to the same polarity as the repeater COS line?

The master control is an 871P1. I do not know if that is the complete model number, that is all I can read. The unit is square (looks like a small table radio) and contains the speaker and volume control plus various control switches at the bottom of the front panel. The repeater did work at one time, but has been out of service for a few years. I do appreciate the troubleshooting information and will take your advice and measure the voltages at the controller. I do have a complete maintenance manual for this repeater, and a schematic. I also have the same for the controller. I will let you know if I solve the problem or not.

One key that may help in troubleshooting IF the squelch in the receiver is staying open. Most FM squelch circuits work by detecting noise and closing the squelch. A signal quiets the noise so the squelch opens. If the receiver has very low sensitivity the noise level may be low enough that the squelch won't close even at the lowest squelch setting.

Check to see if the IFAS board is behaving properly. You should see the RUS and CAS go high when receiving, and they'll go low when the receiver is squelched. The IFAS is the one with the big audio transformer and the metal can that says (DO NOT ADJUST...).

The pins on the IFAS will give you a wealth of info about what's going on in the receiver. Your unsquelched, low level audio will come out of the discriminator on the VSQ HI line. From there it will go through the pot wipers of the volume knob and the squelch knob. If you follow the squelch back on the SQ ARM pin, it will go into one of the black box ICs. That's where it analyzes the audio and determines whether to squelch or not. If you have no audio going back, it won't squelch (because it thinks it's currently receiving a high SINAD, genuine signal). You can get the most info check in the DC voltage levels out of U603, particularly pin 6 (CAS, which is independent of the received CG tone) and pin 8 (RUS, which goes high when receiver is unsquelched AND receiving the correct CG tone).

Check out this GE LBI for info on the IFAS board. The "Circuit Analysis" section does a very good job of explaining how each section works (including the squelch circuit)

The very first thing I'd do is get out your oscilloscope and check these pins...1. Noise or audio on VSQ HI2. Noise or audio on SQ ARM pin (amplitude will go up and down as you play with the squelch knob)3. Noise or audio on pin 2 of U603 ICThen get our your handy-dandy VOM and check these...4. 10V on the 10V pin5. DC voltages around 0 on RUS and CAS (signals used by the repeater interface) when it should be squelched6. DC voltage on RX Mute (which feeds the audio amp, and other things) around 0 when it should be squelched

Be forewarned, replacing parts doesn't always make problems go away. I had to replace an IFAS board 3 times before I found one that worked properly. Had 3 bad parts in stock; all had blown detectors in them.

I would like to thank everyone for there help. I got the repeater working today. It looks like the board I replaced first was an interconnect board ( I said I know very little about repeaters). I replaced the real squelch board and now the repeater works as it should. I was able to download a manual and schematics which really helped.

Now for my next question which I will probably write up as a new topic. What is used and how is the repeater call sign inserted into the repeater? I know that it must send the call sign every 10 minutes.

Thanks again for the information. I am learning a little about repeaters slowly.

Thanks again to everyone. Just for information the controller is a GE Master 2 IDA. I am not sure if it can be programed for the repeater call or not. If it can be programed any information on how to do it would be appreciated. If it con not be programed, someone recommended the new HamGadgets ID=O-Matic controller kit which does the whole the thing for about $38.00 or $48.00 if you want to use voice as well as CW. I would like to program what we have if I can.

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